Review of the $${\Lambda }$$(1405) A curious case of a strangeness resonance

Abstract

During its long-lasting history, the Λ(1405) has become a benchmark for our understanding of the SU(3) hadron dynamics. Starting with its theoretical prediction and later experimental verification, until the most recent debates on the existence of the second broad pole, it emerged as a fruitful research area sparking many theoretical and experimental developments. This review intends to provide the reader with the current status of research on the Λ( 1405)-resonance, reflecting on historical, experimental and theoretical developments. A common database for experimental results and a comparison of most recent theoretical approaches will be provided in the last two parts of this manuscript.

Theory of kaon-nuclear systems

“…[31] that there are actually two poles with I = 0 and S = −1 in the Λ (1405) energy region. This fact has been confirmed in many subsequent studies [12,13,14], including the cloudy bag model [41], meson-exchange model [42], dynamical coupled-channel model [43,44], and Hamiltonian effective field theory [45]. One pole is located near the KN threshold with a narrow decay width.…”

“…Since then a large amount of theoretical and experimental investigations have been devoted to clarify the nature of the Λ (1405) (see Refs. [9,12,13,14]). In particular, recent developments have firmly established the following basic properties of the Λ (1405):…”

“…It is also justified by the N/D method (see Refs. [30,31,9,13]). Because the leading order V WT is a contact interaction, the momentum integration in the loop function involves an ultraviolet divergence.…”

“…We then describe few-body and many-body kaon-nuclear systems, including a discussion of kaon properties in nuclear matter. We also refer here to several review articles covering related topics [7,8,9,10,11,12,13,14].…”

The decay of $N^*$(1895) to light hyperon resonances

“…It is well known that meson-baryon dynamics play an important role in describing Λ(1405) as well (for a recent review see Ref. [25] and to see some well cited articles see Refs. [10,[26][27][28][29] ).…”